Method, equipment and recording device for suppressing pulsed interference in analogue audio and/or video signals

Abstract

Clicks in voice and music signals are removed by detecting and interpolating the click. The use of a permanently set threshold value above the peak value of the audio signal is known for detecting the clicks, and interpolation carried out on the basis of the sample values before and after a click is known for filling them in. Disadvantages of these methods are, on the one hand, that many clicks do not have a larger amplitude than the peak signal and therefore remain undetected, and, on the other hand, interpolation is a highly complex procedure and is limited to a maximum click density. The invention provides for an error signal (e n ) to be determined by adaptive filtering (AF). A sample value is designated as distorted in the input signal (x n ) if the absolute instantaneous value in the error signal (e n ) exceeds a dynamically adapted threshold value. The output signal of the adaptive filtering (y n ) is used as a substitute value for the sample value designated as distorted, specifically both in the case of the signal which is output and in the input values of the adaptive filtering.

What is claimed is:  
     
       1. Recording device for suppressing pulsed interference in analogue audio samples and digitally recording these audio signals, comprising: 
       an analogue/digital converter for forming sample values from the analog audio signals;  
       an apparatus to which the sample values for suppressing pulsed interference are fed, said apparatus comprising means for receiving samples of the audio signal, means for adaptively filtering said received samples, means for deriving an error signal given by the difference between said received samples and said adaptively filtered samples, means for measuring the power of said error signal, means for calculating a threshold value using said error signal power, means for designating a sample as distorted if the error signal exceeds said threshold value, and means for replacing said distorted sample by the output signal of said adaptive filtering; and  
       recording equipment for recording on a digital data carrier, to which equipment the output signal of said apparatus is fed directly or after further processing.  
     
     
       2. Recording device according to  claim 1 , wherein: 
       the device additionally has a playback device for analogue carriers, the analogue audio signal recorded on these analogue data carriers being fed to the analogue/digital converter during playback of the analogue data carriers.  
     
     
       3. Method for suppressing pulsed interferences in audio signal, comprising: 
       receiving samples of the audio signal;  
       adaptively filtering said received samples;  
       deriving an error signal given by the difference between said received samples and said adaptively filtered samples;  
       measuring the power of said error signal;  
       calculating a threshold value using said error signal power;  
       designating a sample as distorted if the error signal exceeds said threshold value; and  
       replacing said distorted sample by the output signal of said adaptive filtering.  
     
     
       4. Method according to  claim 3 , wherein: 
       the adaptation of the adaptive filtering is carried out only at the discrete instants at which the sample value in the input signal is designated as undistorted.  
     
     
       5. Method according to  claim 3 , wherein: 
       the adaptation is suspended if the sample value in the input signal has been designated as distorted.  
     
     
       6. Method according to  claim 3 , wherein: 
       the measurement of the power of the error signal and/or of the input signal is continued only for sample values which have been recognized as undistorted.  
     
     
       7. Apparatus for suppressing pulsed interferences in an audio signal, comprising: 
       means for receiving samples of the audio signal;  
       means for adaptively filtering said received samples;  
       means for deriving an error signal given by the difference between said received samples and said adaptively filtered samples;  
       means for measuring the power of said error signal;  
       means for calculating a threshold value using said error signal power;  
       means for designating a sample as distorted if the error signal exceeds said threshold value; and  
       means for replacing said distorted sample by the output signal of said adaptive filtering.  
     
     
       8. Apparatus according to  claim 7 , wherein: 
       the sample value designated as distorted is also replaced in the input vector of the means for adaptively filtering.